A pelagic ecosystem model calibrated with BATS and OWSI data

Ocean ecosystems play an important role in the global carbon cycle. In this paper: we develop and calibrate a pelagic ocean ecosystem model by simultaneously fitting data from two sites in the North Atlantic: the site of the Bermuda Atlantic Time-series Study (BATS, 32 degrees N, 64 degrees W) and Ocean Weather Ship Station "I" (OWSI, 59 degrees N, 20 degrees-W). These sites differ dramatically in the magnitude and timing of primary production, chlorophyll concentrations, and light and nutrient availabilities. We find that a relatively simple model can be simultaneously fit to ecosystem data at both sites. As in the model of Hurtt and Armstrong (1996, Deep-Sea Research II 43(2-3): 653-683), the fit largely depends on the inclusion of multiple size classes of phytoplankton and detritus and a variable chlorophyll-to-biomass (nitrogen) ratio for phytoplankton. The inclusion of these features in the model enables it to adjust to predict important biological differences temporally within sites and spatially between sites. In addition, the model also includes a phytoplankton self-shading parameter to capture differences in water clarity between sites, and the parameterization of iron limitation at OWSI as a hypothesis for the moderately HNLC condition there. Finally, we suggest that the model performs reasonably well at the Hawaii Ocean Time-series (HOT, 23 degrees N, 158 degrees W), a site where no model calibration was done. (C) 1999 Elsevier Science Ltd. All rights reserved.